This invention relates to low-E coated articles that have approximately the same color characteristics as viewed by the naked eye both before and after heat treatment (e.g., thermal tempering), and corresponding methods. Such articles may in certain embodiments combine: (1) high visible transmission characteristics, (2) good durability before and/or after heat treatment, and/or (3) a low xcex94E* value which is indicative of color stability upon heat treatment (HT). Such coated articles may be used monolithically, in insulating glass (IG) units, laminated window units, vehicle windshields, and/or other vehicle or architectural applications.
Low-emissivity (low-E) coating systems are known in the art. For example, commonly owned U.S. Pat. No. 5,376,455 discloses: glass/Si3N4/NiCr/Ag/NiCr/Si3N4.
The need for substantial matchability (before heat treatment vs. after heat treatment) is known. Glass substrates are often produced in large quantities and cut to size in order to fulfill the needs of a particular situation such as a new multi-window and door office building, vehicle window needs, etc. It is often desirable in such applications that some of the windows and/or doors be heat treated (i.e., tempered, heat strengthened or heat-bent) while others need not be. Office buildings often employ IG units and/or laminates for safety and/or thermal control. It is desirable that the units and/or laminates which are heat treated (HT) substantially match their non-heat treated counterparts (e.g., with regard to color, reflectance, and/or the like, at least on the glass side) for architectural and/or aesthetic purposes. Moreover, in certain example but non-limiting situations, good durability after HT (e.g., scratch resistance and/or chemical durability) may reduce the need for edge deletion so as to reduce window fabrication costs.
Commonly owned U.S. Pat. No. 5,688,585 discloses a solar control coated article including: glass/Si3N4/NiCr/Si3N4. One object of the ""585 patent is to provide a sputter coated layer system that after heat treatment (HT) is matchable colorwise with its non-heat treated counterpart. While the coating systems of the ""585 patent are excellent for their intended purposes, they suffer from certain disadvantages. In particular, they tend to have rather high emissivity and/or sheet resistance values (e.g., because no silver (Ag) layer is disclosed in the ""585 patent).
It has in the prior art been possible to achieve matchability in systems other than those of the aforesaid ""585 patent, but only between two different layer systems, one of which is heat treated and the other is not. The necessity of developing and using two different layer systems to achieve matchability creates additional manufacturing expense and inventory needs which are undesirable.
U.S. Pat. Nos. 6,014,872 and 5,800,933 (see Example B) disclose a heat treatable low-E layer system including: glass/TiO2/Si3N4/NiCr/Ag/NiCr/Si3N4. Unfortunately, when heat treated this low-E layer system is not approximately matchable colorwise with its non-heat treated counterpart (as viewed from the glass side). This is because this low-E layer system has a xcex94E* (glass side) value greater than 4.1 (i.e., for Example B, xcex94a*G is 1.49, xcex94b*G is 3.81, and xcex94L* (glass side) is not measured; using Equation (1) below then xcex94E* on the glass side must necessarily be greater than 4.1 and is probably much higher than that).
U.S. Pat. No. 5,563,734 discloses a low-E coating system including: substrate/TiO2/NiCrNx/Ag/NiCrNx/Si3N4. Unfortunately, it has been found that when high Nitrogen (N) flow rates are used when forming the NiCrNx layers (see the high N flow rate of 143 sccm in Table 1 of the ""734 patent; translating into about 22 sccm/kW), the resulting coated articles are not color stable with heat treatment (i.e., they tend to have high xcex94E* (glass side) values greater than 6.0). In other words, if subjected to HT, the ""734 patent low-E layer system would not be approximately matchable colorwise with its non-heat treated counterpart (as viewed from the glass side). Moreover, ""734 layer systems tend to lack good durability after HT, as they are susceptible to scratching, due to the high nitrogen gas flow used in making the same.
Moreover, it is sometimes desirable for a coated article to have high visible transmission characteristics and/or good durability (mechanical and/or chemical). Unfortunately, certain known steps that are taken to improve visible transmission characteristics and/or pre-HT durability tend to degrade post-HT durability. Thus, it is often difficult to obtain a combination of high visible transmission and good durability.
In view of the above, it will be apparent to those skilled in the art that there exists a need for a low-E coating or layer system that after HT substantially matches in color and/or reflection (as viewed by a naked human eye from the glass side) its non-heat treated counterpart. In other words, there exists a need in the art for a low-E matchable coating or layering system. There also exists a need in the art for a heat treatable system that can combine: (1) high visible transmission characteristics, (2) good durability before and/or after heat treatment, and/or (3) a low xcex94E* value which is indicative of color stability upon heat treatment.
It is a purpose of this invention to fulfill one or more of the above-listed needs, and/or other needs which will become more apparent to the skilled artisan once given the following disclosure.
An object of this invention is to provide a low-E coating or layer system that has good color stability with heat treatment (HT).
Another object of this invention is to provide a low-E matchable coating or layering system.
Another object of this invention is to provide a low-E coating or layering system that combines high visible transmission characteristics, good durability before and/or after heat treatment, and/or a low xcex94E* value which is indicative of color stability upon heat treatment (HT). This combination may be achieved in certain example non-limiting embodiments of this invention by providing a coating including at least one barrier layer that is at least partially nitrided, and which is heat treatable. In this regard, an example coating or layer system may include an IR reflecting layer (e.g., Ag, Au, or the like) sandwiched between first and/or second metal inclusive partially nitrided barrier layers (e.g., of or including NiCrNx or other Ni inclusive alloy). In certain embodiments, both the first and second barrier layers may be partially nitrided (e.g., NiCrNx), while in other embodiments only one of the barrier layers need be partially nitrided (e.g., first barrier layer of or including NiCrNx, and the second barrier layer of or including NiCr). Herein, the term xe2x80x9cnitridedxe2x80x9d means and covers both fully nitrided and only partially nitrided.
Another object of this invention is to provide a coating or layer system designed by adjusting nitriding of at least one barrier layer and adjusting layer thickness(es) in order to obtain a coating or layer system that is capable of combining high visible transmission characteristics, good durability, and/or a low xcex94E* value which is indicative an article that when heat treated is substantially matchable to its non-heat treated counterpart.
Another object of this invention is to fulfill one or more of the above-listed objects.
Certain example embodiments of this invention fulfill one or more of the above-listed objects and/or needs by providing a coated article comprising:
a layer system supported by a glass substrate, said layer system comprising an infrared (IR) reflecting silver layer located between and in contact with first and second metal inclusive barrier layers; and
wherein said coated article is characterized by:
(a) a visible transmittance of at least 70%;
(b) a xcex94E* value (glass side) no greater than 3.5 after or due to heat treatment (HT); and
(c) good mechanical and/or chemical durability before and/or after HT.
Certain other example embodiments of this invention fulfill one or more of the above-listed objects by providing a coated article comprising:
a layer system supported by a glass substrate, said layer system comprising an infrared (IR) reflecting silver layer located between and in contact with first and second metal inclusive barrier layers; and
wherein at least said first metal inclusive barrier layer is at least partially nitrided to an extent so that said coated article has a xcex94E* value (glass side) no greater than 3.5 after or due to heat treatment (HT).
Other embodiments of this invention fulfill one or more of the above listed objects and/or needs by providing a coated article including a layer system supported by a substrate, the coated article comprising:
a first dielectric layer on said substrate;
an IR reflecting layer sandwiched between first and second barrier layers, each of said IR reflecting layer and said barrier layers overlying said first dielectric layer;
a second dielectric layer overlying each of said first dielectric layer, said barrier layers and said IR reflecting layer; and
wherein at least one of said barrier layers comprises a metal nitride that is nitrided to an extent so that the coated article has a xcex94E* value (glass side) no greater than 3.5 after or due to heat treatment (HT).
In certain embodiments, one or both of the barrier layers may comprise NiCrNx.
In other embodiments, certain example embodiments of this invention fulfills one or more of the above-listed objects and/or needs by providing a method of making a coated article, the method comprising:
depositing a layer system on a glass substrate, the layer system including an infrared (IR) reflecting metal layer located between and in contact with first and second metal inclusive layers, at least one of the metal inclusive layers being nitrided to some extent, wherein prior to heat treatment the glass substrate with the layer system thereon has a sheet resistance Rs no greater than 20 ohms/square; and
heat treating the substrate with the layer system thereon so that due to said heat treating the resulting substrate with the layer system thereon has a xcex94E* value (glass side) no greater than 3.5.